1. Field of the Invention
The present invention concerns the molding of diaphragms in the ground, particularly for shallow areas, in order to reinforce and/or waterproof portions of the subsoil.
In particular, the invention concerns the production of continuous barriers which are vertical or sloping, made up of several contiguous plate-like diaphragms.
2. Discussion
The technique has long been known for creating diaphragms in the ground with a substantially plate-like or cylindrical shape by injecting into the ground, through a hollow shaft also functioning as a drill, an appropriate reinforcing and waterproofing substance comprising an aggregating component such as liquid cement, soluble glass (based on sodium silicate), epoxy resins, and possible an adjuvant component such as air or water.
This reinforcing substance is injected into the ground at high pressure while the drill shaft is extracted from the ground, creating either cylindrical columns or vertical plate-like diaphragms formed by the aggregating component mixed with soil.
At their down ends these drill shafts are provided with appropriate means for perforating the ground and with internal canals for the passage of the components of the reinforcement substance. These drill shafts are made up of segments which are joined together successively during the descent, and then are separated during the ascent. This gives rise to numerous inconveniences, such as loss of time in joining and separating the various segments, complicated construction and consequently high cost of these elements. These disadvantages are more pronounced as the depth at which the diaphragms are molded increases.
To create continuous barriers, the known technique provides for the production of barriers made up of a number of contiguous plate-like diaphragms, principally to impede water filtration in certain areas of the ground. However, the production of such barriers presents a number of difficulties because of the inevitable shifting of the axes of the holes with respect to the expected ideal vertical axes. Because of this, it may happen that the vertical edges of the ends of the diaphragms are not together, and this causes discontinuities and interruptions in the barrier; these problems are more pronounced as the depth of the diaphragms is greater. The purpose of this invention, as specified in the claims, is to find a solution for these problems.